SEOUL - A Republic of Korea's army unit staged an anti-terrorism drill Wednesday simulating a toxic gas attack at a Seoul airport, army officials said.

The one-day drill, which involved 400 soldiers, police officers and government officials, was conducted under the scenario of a terrorist gas attack at the Gimpo International Airport in Seoul.

The drill was part of the annual military exercise dubbed Hoguk, which runs through Nov?2 across the country.

The Hoguk Exercise is aimed at enhancing interoperability among the Army, the Navy, the Air Force and the Marine Corps in order to deter localized provocation by the Democratic People's Republic of Korea (DPRK).

The Hoguk drill replaced in 1996 the Team Spirit exercise between the ROK and the United States. Some 500 US troops reportedly plan to take part in the exercise this year.